Means for controlling the supply of liquid fuel to engine or other combustion chambers



Nov. 11, 1958 c, H. an-0 5 2,859,761

MEANS FOR CONTROLLING THE SUPPLY OF LIQUID FUEL TO ENGINE OR OTHER COMBUSTION CHAMBERS Filed April 2, 1956 2 Sheets-Sheet l Nov. 11, 1958 c. H. BOTTOMS 2,859,761

MEANS FOR CONTROLLING THE SUPPLY OF LIQUID FUEL TO ENGINE OR OTHER COMBUSTION CHAMBERS Filed April 2, 1956 2 Sheets-Sheet 2 United States Patent Ofiice MEANS FOR CONTROLLING THE SUPPLY OF LIQUID FUEL TO ENGINE OR OTHER COM- BUSTION CHAMBERS Charles Herbert Bottoms, Toronto, Ontario, Canada, as

signor to Joseph Lucas (Industries) Limited, Birmingham, England This invention relates to means for controlling the supply of liquid fuel to the combustion chamber of a jet-propulsion engine, gas turbine or other apparatus to which air is supplied by a blower, and of the kind which includes an elastic bellows-like capsule arranged to be responsive to blower-air pressure.

When the blower-air pressure is variable over a wide range, its action on a single capsule at low pressure may be inadequate to give the desired sensitivity of control in response to low-pressure variations, and the object of the present invention is to enable this condition to be obviated, so as to ensure the desired sensitivity of response over the whole range of air-pressure variations.

The invention comprises a control means which includes two elastic bellows-like capsules one of which is sensitive to blower-air pressure variations in the upper part of the pressure range, and the other of which is sensitive to pressure variations in the lower part of the range.

In the accompanying drawings, Figures 1 and 2 respectively illustrate two typical forms of control means embodying the invention. Figure 3 illustrates a liquid fuel supply system which includes a control means as shown in Figure 2.

In the example shown in Figure l, a hollow body a has formed therein three compartments b, c, d. The compartment b has an entrance e for air at blowerdelivery pressure, the blower being indicated by 22. In this compartment is contained an evacuated elastic capsule 3 which is pre-stressed and is embraced by a yoke or cage g so that it is rendered responsive only to air pressures in excess of a predetermined amount. One end of this capsule is attached to the control lever 11 of a liquid-operated servo mechanism. In the compartment c is contained another and coaxial evacuated capsule i which at one end is anchored to a wall of the compartment, and which at the other end is attached to the adjacent end of the capsule f by a stem j passing through a seal k between these two compartments. The capsule i is adapted to respond to blower air pressure lower than those to which the capsule f is responsive.

The compartments b, c are in communication with each other through the third compartment d which contains another evacuated capsule m adapted to close a normally open valve 11 for isolating the compartment when the blower-air pressure exceeds a predetermined amount. Also the compartment 0 is open to the atmosphere through a small restricted orifice o.

The mode of action is as follows:

At low blower air pressure the valve 11 is open, and the lever h is actuated in response to pressures in the lower range acting on the capsule i. When the blower air pressure reaches a predetermined amount, it causes the capsule m to close the valve 11, and so isolate the compartment 0. Thereafter, the blower air pressure acts only on the capsule f, and the residual air pressure in the compartment 0 falls to that of the atmosphere by escape through the associated orifice 0. Also in this condition extension of the capsule i is limited by contact of its free end with the adjacent end of the associated compartment.

In the example shown in Figure 2, the arrangement above described is modified inasmuch as the capsules f, i are arranged with their axes parallel with each other and their corresponding ends are connected to the ends of a lever p, the latter being supported at its centre by a sealed pivot q situated between the compartments b, 0 containing these two capsules. The valve-controlling capsule m is contained in a compartment d situated between the other two, this compartment being in communication with the compartment b through a port 20 at one side of the valve 11, and with the compartment c through a port 21 at the other side of the valve.

The means above described may be used to control any convenient form of liquid operated servo mechanism for controlling the rate of supply of liquid fuel as shown, for example, in Figure 3. In this example the lever h carries a closure member s which controls a vent passage t leading from one end of a cylinder u which contains a piston v having therein a restricted orifice w. On this piston is formed or secured a throttle x which varies the elfective area of an orifice y through which liquid fuel passes from a pump z to an outlet 2 connected to the burner in a combustion chamber (not shown), the throttle being attached to the lever h by a spring 3. When the closure member s is in its closed position the throttle x is moved by the spring 3 to the position of maximum restriction of the orifice y. When the closure member is moved by the lever h to an open position, the preponderating liquid fuel-pressure acting on the right hand side of the piston moves the throttle against the action of the spring for increasing the area of the orifice y. Also in the arrangement shown in Figure 3, the liquid pressure difference between the inlet and outlet side of the orifice y is utilized to control the pump output. Passages 4, 5 conduct liquid to opposite sides of a diaphragm 6 which is loaded by a spring 7 and which serves to actuate a lever 8 carrying a closure member 9 which controls a vent 10 communicating with a cylinder 11. This cylinder contains a piston 12 provided with a restricted orifice 13 and loaded by a spring 14. The piston is connected by a rod 15 to any convenient device for controlling the pump output. When the vent 10 is closed the spring 14 moves the piston 12 in the direction for increasing the pump output, and when open, the preponderating liquid fuel pressure acting on the left hand side of the piston moves the latter in the direction for decreasing the pump output.

By the use of resilient elastic capsules each adapted to respond as above described to different blower air pressures, sensitive response to pressures which vary over a wide range can be ensured in a simple and satisfactory manner.

What I claim is:

1. Means for controlling the supply of liquid fuel to a jet-propulsion engine, gas turbine, or other apparatus to which air is supplied by a blower, comprising in combination a first chamber provided with an entrance for blowerair, a first bellows-like capsule mounted in the first chamber and adapted to respond to blower-air pressure variations in the upper part only of the pressure range, fuelfiow varying means including a control member operatively connected to the first capsule, a second chamber communicating with the first chamber and provided with a restricted air outlet, means responsive to blower-air pressure for interrupting communication between the first and second chambers when the pressure in the first chamber attains a predetermined value, a second elastic bellowslike capsule mounted in the second chamber and adapted to respond to blower-air pressure variations in the lower part of the pressure range, and means interconnecting i Patented Nbv.'11, 1958 the, capsulessso that response of the secondcapsule to responsive to blower-air pressure; the valve being conbloWer-air pressure variations is transmitted through the nected to and operable by the third capsule. firsfcapsule to the said control 'member. V a

2. Means according to claim 1, and having a third R f r nces Cited in the file of this patent chamber through which the, first chamber communicates 5 withthe second chamber under the controlof a valve UNITED STATES'PATENTS constitutingthe means forsinterrupting communication 2,372,306 Adair Mar. 27, 1945 between the first and second chambers, and ,a third elastic 2,747,596 Ifield May 29, 1956 bellows-like capsule mounted in the third chamber and 

